In many parts of California, reminders abound that the American West is running out of water. “Bathtub rings” mark the shrinking of the state’s biggest reservoirs to some of their lowest recorded levels. Fields lie fallow, as farmers grapple with an uncertain future. A bed-and-breakfast owner spends $5 whenever a tourist showers. But not in San Diego County. In this coastal desert metropolis, life has stayed mostly the same for residents already accustomed to conserving what they have long treated as a precious resource.